Personal communication service (PCS) is a service in which subscribers, rather than locations or telephone stations, are assigned a personal telephone number. Calls placed to a subscriber's personal telephone number are routed to the subscriber at a telephone near that subscriber's current location. In order to provide a subscriber with such a personal communication service, e.g., as disclosed in U.S. Pat. No. 4,313,035, issued to Jordan, et al, the system providing the service (PCS system) must be supplied with the telephone number of a telephone near the subscriber's current location to which it should route calls placed to his personal telephone number. Each time the subscriber changes his location, the telephone number to which calls placed to his personal telephone number are routed must be changed. This requires the subscriber to call into the PCS system and to supply the telephone number to which his calls should currently be routed. Constantly having to call in to the PCS system can be tiresome, and supplying a ten-digit telephone number each time a subscriber changes his location is cumbersome.
To overcome these drawbacks, one prior art solution is to program a sequence of telephone numbers at any one of which the personal telephone service subscriber might be reached. The telephone numbers in a sequence are typically those of locations where a person is likely to be at various times throughout the day, such as "home," "car phone," "office," "pager," etc. When a call is made to the subscriber's personal telephone number, the PCS system attempts to complete the call by sequentially routing the call to each telephone number of the sequence. This process continues until: (a) the call is answered; (b) the call is abandoned; (c) the line associated with the telephone number is determined to be busy; or (d) until a predetermined period of time has elapsed. However, requiring the sequence of calls to be set by the subscriber in advance, and being the same for all callers, is inflexible.
Certain existing systems also offer various alternative means to attempt to reach a subscriber should the sequential routing of the call not be successful including, of course, the well known use of voice mail, E-mail, etc. However, such alternative means are not always successful when the need for rapid communication is necessary, as a subscriber is usually unaware he, or she, has received a voice mail message until the subscriber checks the voice mail center.
Another problem occurs when the central platform automatically redirects calls to a subscriber, based on preprogrammed subscriber schedule changes. Often, a subscriber may forget the preprogrammed automatic schedule changes, and be unaware that his or her calls are being redirected unless reminded that a schedule change has occurred.
The instant invention solves these problems through the use of an out-of-band signaling scheme on an ancillary signaling path that immediately alerts a subscriber to incoming calls, voice mail messages and schedule changes, as well as certain alarm conditions.
A related applicaiton of interest is Ser. No. 08/023,223, filed on Feb. 26, 1993, and allowed on Nov. 15, 1994, which patent is assigned to the same assignee as is the instant application.